Chemical Reactions

What is a Chemical Reaction? A chemical reaction is the process by which a chemical change occurs. A chemical change is a change in which one or more substances combine or break apart to form new substances.

Describing Chemical Reactions We write out a chemical reaction like this: CH 4 + O 2 CO 2 + H 2 O Chemical Equation Reactants The substances that go IN to a chemical reaction. “The stuff that reacts” Products The substances that come OUT of a chemical reaction. “What the reaction produces”

Reactants and Products In a chemical reaction, the total mass of the reactants must equal the total mass of the products. Reactant 1 + Reactant 2 Product 1 + Product 2 38 grams Law of Conservation of Mass Why? Because every atom which goes into a chemical reaction is still present at the end of a reaction.

Parts of a Chemical Reaction CH 4 + O 2 CO 2 + H 2 O

So What’s Really Happening? During a chemical reaction: » Bonds between atoms are broken. » New bonds form. » The new chemical compositions result in new substances. – To put it more simply… The atoms rearrange “The atoms rearrange”

“The Atoms Rearrange” HH Hydrogen and Oxygen form Water H 2 + O 2 = H 2 O OO HH 2H 2 + O 2 = 2H 2 O Balanced Equation

2 NaCl + CO 2 + H 2 O From Your Lab Mixture 1: Hydrochloric acid and Sodium carbonate 2 HCl + Na 2 CO 3 Products: Sodium Chloride (Table Salt) Carbon Dioxide Water Reactants: Hydrochloric acid Sodium Carbonate

2 NaCl + CO 2 + H 2 O From Your Lab Mixture 1: Hydrochloric acid and Sodium carbonate 2 HCl + Na 2 CO 3 H – Hydrogen Cl – Chlorine Na – Sodium C – Carbon O - Oxygen

From Your Lab Mixture 7: sodium hydroxide and copper sulfate 2 NaOH + CuSO 4 Cu(OH) 2 + Na 2 SO 4 Mixture 6: sodium hydroxide and calcium chloride 2 NaOH + CaCl 2 2 NaCl + Ca(OH) 2 The atoms REARRANGE

REVIEW A chemical reaction leads to a chemical ______. –This produces ______ substances. To represent what happens in a chemical reaction we write a chemical ___________. The substances that go INTO a reaction are called _____________. The substances that come OUT of a reaction are called _____________. The Law of Conservation of _______ says that the total ______ of the reactants must equal the total ______ of the products.

REVIEW During a chemical reaction: –The _______ between atoms are broken. –New _______ form. –The new chemical compositions result in new substances. In other words, the atoms Re-____________.